Vat dye pigment pad process for cellulose ester textiles using a water-miscible organic swelling agent in the alkaline hydrosulfite reducing bath



Patented Dec. 2, 1952 UNITED STATES PATENT OFFICE VAT DYE PIGMENT PAD PROCESS FOR CELLULOSE ESTER TEXTILES USING A WATER-MISCIBLE ORGANIC SWELLING AGENT IN THE ALKALINE HYDROSUL FITE REDUCING BATH George C. Ward and William T. Haggerty; J r.,

Cumberland, Md.,.assignors to Celanese Corporation of America, a corporation of Delaware No Drawing; Application December 15, 1948,

Serial No. 65,518

7 Claims. 1

This invention relates to the dyeing of textile materials, and relates more particularly to the dyeing of textile materials havinga basis of cellulose acetate or other organic acid ester of cellulose textile material.

An object of this invention is the provision ofan improved process for the dyeing of cellulose acetate or other organic acid ester of cellulose textile materials in shades of superior color fastness.

Another object of this invention is to provide a process for the dyeing of textile materials having a basis of cellulose acetate or other organic acid ester of cellulose with vat dyestuffs without impairing the physical properties of said materials by excessive saponification, and the like.

Other objects of this invention will appear from the following detailed description.

Vat dyestuffs may be appliedto cellulose acetate or other organic acid ester of cellulosetextile materials in the reduced or leuco form in a strongly alkaline bath and the vat dye then fixed in the fabric by introducing the treated textile material into a suitable oxidizing bath which oxidizes the dye from the colorless leuco form to the colored form. Alternatively, the unreduced dye in the pigment or colored form may be padded on to the textile material, the dye reduced to the leuco form by entering the textile material carrying the dyestuff into an alkaline reducing bath and the reduced dyestufi on the fabric then oxi dized back to the colored form in a suitable oxidizing bath. This latter method of dyeing with vat dyestufisis commonly known in the art as the pigment-pad method of dyeing. In order to effect a thorough reduction and penetration in the pigment-pad method somewhat prolonged immersion in the'strongly alkaline vat is necessary. Such prolonged immersion in a strongly alkaline medium is undesirable since there is always present the danger of injury to-the organic acid ester of cellulose materials being dyed. The injury may comprise a weakening and loss of weight-of the fibers due to the fact that the organic acid ester of cellulose fibers may undergo some degree of saponification; in the fibers is, of course, highly disadvantageous.

We have now found that if a water-miscible organic solvent or swelling agent for the cellulose acetate or other organic acid ester of cellulose textile material is incorporated in the strongly alkaline bath employed for reducing the vat dyestuff from the pigment to the leuco form in the pigment-pad process of dyeing cellulose acetate or other organic acid ester of cellulose textile materials, the period of immersion in the alkaline reducing bath may be considerably decreased. Thus, improved colorations are obtained on sub- Such a change sequent oxidation of the leucovat dyestuff on the textilematerial due to improved penetration,

As examples of water-miscible organic compounds having a solvent or swelling action on the cellulose acetate or other organic acid ester of cellulose textile materials which may be employed in accordance with our novel process there may be mentioned lower aliphatic alcohols, such as methyl alcohol, ethyl alcohol, isopropyl alcohol, butyl alcohol or amyl alcohol, ketones such as acetone or methyl ethyl ketone or a bifunctional compound such as diacetone alcohol. Preferably, the water-miscible organic compound comprises from 10 to 50% by weight of the reducing bath employed.

Thus, indyeing. cellulose acetate or other organic acid ester of cellulose textile materials by our novel process, the vat dyestuii employed, in finely-divided, unreduced pigment form, is dispersed in an aqueous medium with the aid of a suitable dispersing agent and the textile material to be dyed then padded'with the aqueous dispersion of dyestuff. Dispersing agents such as alkyl aryl sulfonates, sulfated or sulfonated fatty acid amides or sodium alkyl naphthalene sulfonates are suitable. The textile material, after being padded with the aqueous dispersion, may then be dried, if desired, although drying is not essential. After impregnation, reduction of the vat dye on the textile material to the leuco or colorless form is then eifected by passing the textile material through the alkaline reduction bath containing the organic solvent or softening agent for the cellulose acetate or other organic acid ester of cellulose material.

The aqueous dispersion of the finely-divided vat dyestuil may be applied to the textile material conveniently by mechanical impregnation, i. e., by padding, prior to reduction in the alkaline reducing bath. Advantageously, the dispersion is maintained at a temperature of about 40 to C. during the padding operation. The dyestuff may be reduced to a finely-divided form by grinding operations, as in a ball-mill. Usually, the dyestuii is ground or milled together with from 0.25 to 5% by weight of the desired dispersing agent and the mixture added to water in an amount necessary to form a dyebath of the desired concentration. The concentration of dyestuff in the dyebath may vary depending on the depth of shade desired in the cellulose acetate or other organic acid ester of cellulose materials being dyed. Usually, dyebaths containing from about 0.5 to 5% by weight of dyestuff on the weight of the dyebath are satisfactory.

The textile material, after being padded with the aqueous dyebath dispersion, is then subjected to the reducing action of the alkaline reducing bath containing the organic solvent or softening agent. The reduction bath employed contains, in addition to the organic solvent or softening agent for the cellulose acetate or other organic acid ester of cellulose material, an alkali, such as caustic soda, together with a suitable alkaline reducing agent, such as sodium hydrosulfite. Preferably, the reducing bath contains from 0.2 to 1.2% by weight of caustic soda, 0.2 to 1.2% by weight of sodium hydrosulfite, 50 to 80% by weight of water and to 50% by weight of the organic solvent or softening agent. The temperature of the reducing bath during reduction of the vat dyestuff may be at from 30 to 60 C. The alkaline reducing bath is, preferably, also applied by paddin operations. The period of immersion in the reducing bath is usually from to 90 seconds. After reduction, the textile material is then washed, usually with cold water, and the leuco .vat dye present thereon then oxidized to the colored form. The use of the Williams unit in the dyeing of textile materials by our novel process has been found to yield excellent results.

The oxidation of the leuco vat dye is effected with a dilute aqueous solution of a suitable oxidizing agent. Suitable oxidizing agents which may be employed are, for example, hydrogen peroxide, sodium perborate, sodium dichromate and acetic acid, but we preferably employ a /2 to 2% by weight aqueous solution of hydrogen peroxide as the oxidizing agent. The temperature of the oxidizing bath may be maintained at from 40 to about 50 C. and the textile material immersed therein for about 15 to 90 seconds to effect the desired oxidation of the leuco vat dyestuff to the colored form. After oxidation is completed, the textile material is rinsed in cold water and then scoured on a jig, rinsed, dried and steamed on a tenter.

Any suitable vat dyestuif may be employed in our process and examples of suitable vat dyes are:

Calcosol Brown G Paste Calcosol Fast Yellow Pst.

Indanthrene Blue BCSN Dbl. Pst. (C. I. 1114) Indanthrene Dark Blue BOD Pst.

Indanthrene Rubine RAF Conc. Pst. Indanthrene Red FBBA Indanthrene Brown RAP (C. I. 1151) Indanthrene Olive RAP Pst. (C. I. 1150) Indanthrene Violet FF'BNA Pst.

Indanthrene Yellow GD Dbl. Fine Pst. New

Cibanone Grey RA Pdr. Amanthrene Pink FF Pst.

Ciba Brown G (C. I. Pr. 121) Ciba Blue 2B Micro Pdr. (C. I. 1184) Ciba Scarlet G Pst. (C. I. 1128) In order further to illustrate our invention, but without being limited thereto, the following examples are given:

Example I A cellulose acetate fabric having a construction consisting of 300 denier, 80 filament acetonesoluble cellulose acetate yarns in the warp and an 18/2 spun cellulose acetate yarn in the filling is padded with a dyebath of the following composition at a temperature of 40 C.:

Parts by weight Calcosol Brown G Paste 15 Calsosol Fast Yellow Paste 3 Sulfanol R. (sulfated fatty acid amide) 1 Water 500 4 The dyebath is maintained at a temperature of 40 C. during padding and the nip of the pad adjusted to permit 75% on the weight of the fabric of the dyebath to remain thereon. The padded fabric is then dried and entered into a reducing bath of the following composition:

Parts by weight Sodium hydroxide 15 Sodium hydrosulfite 18 Diacetone alcohol 750 Water 1670 The reducing bath is maintained at a temperature of 60 C. and the fabric passed through the reducing bath at such a speed that the immersion time of the fabric in the reducing bath is about 22 seconds. The reduction of the vat dye to the leuco form is completed in this period and the fabric is then washed in cold Water and immersed in a 0.75% by weight aqueous solution of hydrogen peroxide at 40 C. for 20 seconds to oxidize the vat dyestulf from the leuco to the colored form. The dyed fabric is rinsed again in cold water, scoured on a jig, rinsed in hot water, dried and steamed on a tenter. The fabric is dyed in a level sand shade.

Example II The cellulose acetate fabric consisting of 300 denier, filament acetone-soluble cellulose acetate yarns in the warp and an 18/2 spun cellulose acetate yarn in the filling is padded with a dyebath of the following composition at a temperature of 50 C.

Parts by weight Cibanone Grey RA Pdr 23.7

Indanthrene Violet FFBNA Pst 0.84

Alkanol WXN (Sodium hydrocarbon sulfonate) 1 The dyebath is maintained at a temperature of 50 C. during padding and the nip of the pad adjusted to permit 50% on the weight of the fabric of the dyebath to remain thereon. The padded fabric is then entered in a reducing bath of the followin composition:

Parts by weight Sodium hydroxide 15 Sodium hydrosulfite I 18 Diacetone alcohol 750 Water 1670 The reducing bath is maintained at a temperature of 60 C. and the fabric passed through the reducing bath at such a speed that the immersion time of the fabric in the reducing bath is about 30 seconds. The reduction of the vat dye to the leuco form is completed in this period and the fabric is then washed in cold water and immersed in a by weight aqueous solution of sodium perborate at 40 C. for 20 seconds to oxidize the vat dyestuif from the leuco form to the permanent color. The dyed fabric is rinsed again in cold water, scoured on a jig, rinsed in hot water, dried and steamed on a tenter frame. The fabric is dyed a level, medium grey shade.

While the novel process of our invention has been more particularly described in connection with the dyeing of cellulose acetate textile materials, equally valuable results are obtained when dyeing textile materials having a basis of other organic acid esters of cellulose. Examples of other organic acid esters of cellulose are cellulose propionate, cellulose butyrate, cellulose acetate-propionate and cellulose acetate-butyrate.

Other organic derivatives of cellulose, such as ethyl cellulose, benzyl cellulose or other cellulose ethers may also be dyed effectively by our novel process although the problem of saponification is not as serious when dyeing said materials.

It is to be understood that the foregoing detailed description is given merely by way of illustration and that many variations may be made therein without departing from the spirit of our invention.

Having described our invention, what we desire to secure by Letters Patent is:

1. In a pigment pad process for the dyeing of organic acid ester of cellulose textile materials with the vat dyestuif wherein a vat dye is applied to said textile material in an unreduced form, the vat dye reduced to the leuco form in an alkaline reducing bath and then oxidized on the textile material to the colored form, the improvement which comprises employing a strong alkaline reducing bath, containing from 0.2 to 1.2% by weight of caustic soda, from 0.2 to 1.2% by weight of sodium hydrosulphite, from 50 to 80% by weight of water and 20 to 50% by weight of a water-miscible organic swelling agent for the cellulose acetate textile material, and subjecting the textile material to the action of said reducing bath, at a temperature of from 30 to 60 C., for from to 90 seconds.

2. In a pigment pad process for the dyeing of organic acid ester of cellulose textile materials with the vat dyestuff wherein a vat dye is applied to said textile material in an unreduced form, the vat dye reduced to the leuco form in an alkaline reducing bath and then oxidized on the textile material to the colored form, the improvement which comprises employing a strong alkaline reducing bath, containing from 0.2 to 1.2% by weight of caustic soda, from 0.2 to 1.2% by weight of sodium hydrosulphite, from 50 to 80% by weight of water and to 50% by weight of a lower aliphatic alcohol, and subjecting the textile material to the action of said reducing bath, at a temperature of from to 60 (3., for from 15 to 90 seconds.

3. In a pigment-pad process for the dyeing of organic acid ester of cellulose textile materials with the vat dyestuff wherein a vat dye is applied to said textile material in an unreduced form, the vat dye reduced to the leuco form in an alkaline reducing bath and then oxidized on the textile material to the colored form, the improvement which comprises employing a strong alkaline reducing bath, containing from 0.2 to 1.2% by weight of caustic soda, from 0.2 to 1.2% by weight of sodium hydrosulphite, from to 80% by weight of water and 20 to 50% by weight of a lower aliphatic ketone, and subjecting the textile material to the action of said reducing bath, at a temperature of from 30 to C., for from 15 to 90 seconds.

4. In the pigment-pad process for the dyeing of cellulose acetate textile materials with a vat dyestufi wherein a vat dye is applied to said textile material in an unreduced form, the vat dye reduced to the leuco form in an alkaline reducing bath and then oxidized on the textile material to the colored form, the improvement which comprises employing a strong alkaline reducing bath, containing from 0.2 to 1.2% by weight of caustic soda, from 0.2 to 1.2% by weight of sodium liydrosulphite, from 50 to 80% by weight of water and 20 to 50% by weight of a water-miscible organic swelling agent for the cellulose acetate textile material, and subjecting the textile ma- 6 terial to the action of said reducing bath, at a temperature of from 30 to 60 0., for from 15 to 90 seconds.

5. In the pigment-pad process for the dyeing of cellulose acetate textile materials with a vat dyestuff wherein a vat dye is applied to said textile material in an unreduced form, the vat dye reduced to the leuco form in an alkaline reducing bath and then oxidized on the textile material to the colored form, the improvement which comprises employing a strong alkaline reducing bath, containing from 0.2 to 1.2% by weight of caustic soda, from 0.2 to 1.2% by weight of sodium hydrosulphite, from 50 to by weight of water and 20 to 50% by weight of diacetone alcohol, and subjecting the textile material to the action of said reducing bath, at a temperature of from 30 to 60 0., for from 15 to seconds.

6. In the pigment-pad process for the dyeing of cellulose acetate textile materials with a vat dyestuff wherein a vat dye is applied to said textile material in an unreduced form, the vat dye reduced to the leuco form in an alkaline reducing bath and then oxidized on the textile material to the colored form, the improvement which comprises employing a strong alkaline reducing bath, containing from 0.2 to 1.2% by weight of caustic soda, from 0.2 to 1.2% by weight of sodium hydrosulphite, from 50 to 80% by weight of water and 20 to 50% by weight of ethyl alcohol, and subjecting the textile material to the action of said reducing bath, at a temperature of from 30 to 60 C. for from 15 to 90 seconds.

7. In the pigment-pad process for the dyeing of cellulose acetate textile materials with a vat dyestuff wherein a vat dye is applied to said textile material in an unreduced form, the vat dye reduced to the leuco form in an alkaline reducing bath and then oxidized on the textile material to the colored form, the improvement which comprises employing a strong alkaline reducing bath, containing from 0.2 to 1.2% by weight of caustic soda, from 0.2 to 1.2% by weight of sodium hydrosulphite, from 50 to 80% by weight of water and 20 to 50% by weight of isopropyl alcohol, and subjecting the textile material to the action of said reducing bath, at a temperature of from 30 to 60 C., for from 15 to 90 seconds.

GEORGE C. WARD. WILLIAM T. HAGGERTY, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,738,978 Whitehead Dec. 10, 1929 1,963,974 Ellis June 26, 1934 1,968,819 Dreyfus Aug. 7, 1934 2,248,048 Alla-n July 8, 1941 2,518,153 Laughlin Aug. 8, 1950 FOREIGN PATENTS Number Country Date 578,212 Great Britain June 18, 1946 847,107 France June 26, 1939 928,944 France June 16, 1947 OTHER. REFERENCES Rayon Textile Monthly for March 1947, page (158).

Rayon for September 1946, page (496). Ame-r. Dyes. Rep. for May 21, 1945, page P212. 

1. IN A PIGMENT PAD PROCESS FOR THE DYING OF ORGANIC ACID ESTER OF CELLULOSE TEXTILE MATERIALS WITH THE VAT DYESTUFF WHEREIN A VAT DYE IS APPLIED TO SAID TEXTILE MATERIAL IN AN UNREDUCED FORM, THE VAT DYE REDUCED TO THE LEUCO FORM IN AN ALKALINE REDUCING BATH AND THEN OXIDIZED ON THE TEXTILE MATERIAL TO THE COLORED FORM, THE IMPROVEMENT WHICH COMPRISES EMPLOYING A STRONG ALKALINE REDUCING BATH, CONTAINING FROM 0.2 TO 1.2% BY WEIGHT OF CAUSTIC SODA, FROM 0.2 TO 1.2% BY WEIGHT OF SODIUM HYDROSULPHITE, FROM 50 TO 80% BY WEIGHT OF WATER AND 20 TO 50% BY WEIGHT OF A WATER-MISCIBLE ORGANIC SWELLING AGENT FOR THE CELLULOSE ACETATE TEXTILE MATERIAL, AND SUBJECTING THE TEXTILE MATERIAL TO THE ACTION OF SAID REDUCING BATH, AT A TEMPERATURE OF FROM 30 TO 60* C., FOR FROM 15 TO 90 SECONDS. 